Recording is one of essential functions of a handheld terminal device such as a mobile phone. A terminal device (also referred to herein as pickup apparatus) 100 shown in FIG. 1 is used as an example. In the pickup apparatus 100, a microphone 101 first performs pickup, and converts a sound signal into an analog electrical signal. Then, the analog electrical signal is transmitted to an amplifier 102, and the amplifier 102 amplifies/adapts a weak analog electrical signal output by a microphone into a system specification range. The amplified analog electrical signal is then transmitted to an Analog-to-Digital Converter (ADC) 103 to implement digitalization conversion of the analog electrical signal. Finally, the recorded data is saved in a memory 104 in the pickup apparatus 100 to facilitate playback later.
For a pickup function such as the foregoing recording, a wide dynamic recording range is an important indicator for measuring pickup quality. For an ideal pickup device, highest volume does not cause that a collected signal is saturated or clipped or even device damage, and lowest volume may also be identified, that is, volume of different amplitudes may be faithfully recorded. As shown in FIG. 2, a maximum sound pressure level (SPL) that may be supported by a common pickup device is generally 115 decibels (dB) to 210 dB, which corresponds to an SPL of a common sound source. Therefore, in a scenario in which a SPL of a sound source is greater than 210 dB— (for example, a live concert), saturation distortion occurs in an audio signal output by a microphone or a subsequent processing unit in a pickup device, and as a result the pickup device cannot completely perform pickup. On the other hand, in a scenario of a low-volume signal, volume of the sound source is relatively low, and the SPL decreases as a distance between the SPL and the sound source increases. Therefore, to implement pickup of a low-volume signal, the pickup device needs to have high sensitivity and a high signal-to-noise ratio. The high sensitivity means that an extremely weak signal is enough to drive vibrating diaphragm vibration of the microphone for conversion into an electrical signal, and the high signal-to-noise ratio means low enough line noise such that a weak signal is not overwhelmed by noise.
As shown in FIG. 1, a typical pickup apparatus includes a microphone, an amplifier, and an ADC. In this case, it is difficult to consider three indicators at the same time supported maximum sound pressure, a signal-to-noise ratio, and sensitivity. For example, if the pickup device is expected to obtain a high enough signal-to-noise ratio and high sensitivity in a pickup scenario of low volume or typical volume, an electrical signal obtained by means of conversion by the microphone rapidly becomes strong with the enhancement of sound pressure in a case of high sound pressure to exceed a sound pressure supporting capability of the pickup device. In this case, even though a vibrating diaphragm of the microphone does not perform clipping, an analog circuit of a back end performs clipping. However, if the pickup device is expected to have a relatively low signal-to-noise ratio and sensitivity in a scenario of high volume, in a case of low volume, an electrical signal converted by the microphone is overwhelmed by a noise signal and cannot be identified. In conclusion, a technical problem that needs to be urgently resolved in the art is to implement pickup of a relatively large dynamic range such that the pickup device may be applied in both a scenario of high volume and a scenario of low volume.